β22放大器制作全攻略要的就是完成度和原汁原味与各位DIY分享全文更新完毕

ray23 · 发表于 2008-12-14 21:48

期待

燃烧我的罪恶 · 发表于 2008-12-14 21:49

原帖由 发烧龙 于 2008-12-14 21:42 发表
套件在哪里买？短信告诉我下好么？谢谢。

β22爱好者QQ群 63247767

燃烧我的罪恶 · 发表于 2008-12-14 22:08

谢谢O大大帮忙更新完图片全文完毕

iop · 发表于 2008-12-14 22:31

四川老乡的贴要顶~

的确是好东西！

燃烧我的罪恶 · 发表于 2008-12-14 23:08

原帖由 iop 于 2008-12-14 22:31 发表
四川老乡的贴要顶~
的确是好东西！

谢谢了

石城 · 发表于 2008-12-14 23:27

好。功力深厚

millwood · 发表于 2008-12-14 23:43

原帖由 燃烧我的罪恶 于 2008-12-14 20:28 发表

结构上是这样的
但是国内就是不容易购买到
我曾经问过很多家有些甚至天价啊几十元的报价

jfets are typically sold in grades based on their Idss. so you just need to buy a few of them in the same grade and hand match them.

2sk170 or lsk170 are very very good jfets for such purposes.

millwood · 发表于 2008-12-15 00:08

原帖由 燃烧我的罪恶 于 2008-12-14 20:28 发表

给点改进意见啊

how you want to modify it depends a lot on what you want with this amp and how you approach audio in general.

just some obvious design considerations, based on the first schematic in post #2:

1) you should never use a mosfet without gate stoppers. R8=R26=11 - 470ohm based on your mosfet and for this particular pair, you can go lower but not having one is asking for trouble.
2) R14/R21: unless you want to use this as a power amp, use higher R14/R21 to mminimize distortion andn provide better thermal stability. 4.7 - 47ohm would be a good starting point.
3) C6/C7/C12/C13 are on the small side. but keep them if your amp isn't oscillating.
4) Q12/Q13: the use of BJTs to compensate mosfet output devices tends to result in overcompensation. I would use a Vgs multiplier here - replace those transistors with the same transistors as your output device.
5) R35/R34: this is not a CFB amp and it doesn't benefit from absurdly small feedback resistors. not to mention those astronomical gain numbers for a headphone amp.
6) C19: don't use C19 unless you have exhausted anything else.
7) R18: too large. it doesn't nothing but make the amp susciptible to interference and introduces thermal noise. for perfect offset cancellation, R18=R34//R35 but since you are using jfets, that may not be as big of an issue here. I would make sure that it is less than 47k.
8) R9/R10/R19/R24: a little bit high, especially for jfets but shouldn't be a big deal.
9) C2/C16: make sure you use a small and fast capacitor. I typically use polyester caps here.

if you step back, you will notice that this is an overkill for a headphone amp. you wouldn't even come close to remotely using a tiny fraction of this amp's capabilities to drive most headphones.

will you get good sound out of it? yes.
will you get more than what you could out of a much simpler design? yes.
will you be able to tell them apart? highly unlikely.

the design is a "techno" design in that it pursues the best measurement, regardless if such measurement brings any betterment to the sound, or at what cost (both monetary or effortwise).

it is designed by a very technically superior designer who has minimal understanding of how to design a beautiful sounding amp.

I will take any of Pass' designs over this one (b22), even though the Pass designs are far inferior to this amp technically.

I was recently discussing this very issue and the analogy I used is that a great race car driver knows when to slow down and a new race car driver only wants to drive fast.

hope that helps.